Enhanced channel hopping sequence

ABSTRACT

A system and method for enhanced channel hopping sequence is described. A pseudo random channel hopping sequence is redistributed using certain system specific parameters for separating adjacent transmission channels within a predetermined number of consecutive transmission channel numbers in the random channel hopping sequence to improve inter-channel interference between adjacent transmission channels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/983,136, filed Dec. 29, 2015, which claims priority to U.S.Provisional Patent Application No. 62/165,621, filed May 22, 2015, theentirety of each of which is herein incorporated by reference.

TECHNICAL FIELD

This disclosure relates generally to the field of wireless communicationand more specifically to wireless transmission using frequency hoppingsequences.

BACKGROUND

Channel Hopping is a mechanism by which a transmitter ‘hops’ through ormoves to different channels (frequency bands) during its normaloperation. A data exchange between nodes may happen on a single channelor multiple channels depending on the different protocols. Althoughnodes hop on multiple channels, a single transmission and receptionhappens only on one of those channels. The channel hopping increasesnetwork throughput by promoting simultaneous data transfer over multiplechannels between different pairs of nodes and improves reliability inrough channel conditions by exploiting the channel diversity.

One application of channel hopping is Frequency Hopping Spread Spectrum(FHSS). FHSS is a method of transmitting radio signals by switchingcarriers among many frequency channels using a pseudorandom sequenceknown to both transmitter and receiver. In such systems, signaltransmitters rapidly switch carrier frequencies using various “hopping”schemes to avoid the problem of signal interference at a particularfrequency. However, for such systems to operate, the TX and RX pair haveto align on the spreading sequence to be used as it requires PHY levelsynchronization.

Other methods to achieve channel hopping involves changing of channel atPHY level as directed by MAC. However, a single frame exchange isperformed only on one channel or few channels. Frequency hopping allowstransmitting devices to use various carrier frequencies to enhance thesignal transmission in various different transmission environments. Infrequency hopping systems, signals experience different sets ofinterference during each “hop” and thus avoid possible constantinterference at a particular frequency. Frequency hopping is commonlyused for transmission in Wireless Local Area Networks (WLAN), GlobalSystem for Mobile Communications (GSM), Bluetooth, and various othercommunication systems. Channel hopping wireless transmission systemprotocols typically have a retransmission mechanism to retransmit lostpackets. When channel hopping is used, subsequent retransmissions canuse a different channel in the channel hopping sequence. This helpsavoiding channel interference that may have existed in the previouschannel causing the packet loss.

Channel hopping can be achieved through many different implementations.Some of the common implementations include synchronous method such asTime Slotted Channel Hopping (TSCH) or asynchronous method such asun-slotted channel hopping as defined by Part 15.4, Low-Rate WirelessPersonal Area Networks (LR-WPANs), IEEE 802.15.4e, 2012. Channel hoppingschemes are used for various applications for example, Wi-SUN Alliancehas proposed a Field Area Network (FAN) specification that specifies theuse of channel hopping for smart grid applications.

Existing channel hopping schemes have following requirements:

-   -   The next channel in frequency hopping sequence must be at least        pseudo random.    -   All channels must be equally distributed.    -   The random sequence must be repeatable so that it can be        communicated to receivers.        These channel hopping schemes do not account for Inter Channel        Interference (“ICI”). When a channel is not suitable for        transmission due to interference, then typically it affects the        data packet transmission in adjacent channels or even a few        channels adjacent to it as well. Some of the commonly known        random sequences for channel hopping mechanism are Linear        Feedback Shift Register (LFSR) and Linear Congruential Generator        (LCG).

These schemes generate pseudo random sequences; however, they do notaccount for inter channel interference. Although the sequences arerandom, they do allow for next channels in the list to be close to thecurrent channel, for example, if a packet is dropped due to bad channelconditions, then the possibility is that the retransmission may occur ina channel that is closer to the previous channel and the retransmissionmay also fail due to the inter channel interference from the previouschannel. Most wireless systems have retransmission limits fortransmission efficiency purposes and if a packet retransmission reachesthe maximum limit for retransmission, then the entire transmissionsession has to be restarted. This results in multiple transmissionsessions and causes waste of system resources and poor bandwidthutilization.

Referring to FIG. 1, an example of conventional implementation of LinearFeedback Shift Register scheme is illustrated. The example illustratesthe percentage of adjacent channel interference across number of channelhopping separations (N_(sep)) for a LFRS sequence when the number ofretransmissions limit is set to 6. The amount of adjacent channelinterference in the sequence was computed by measuring the number ofchannels in a sequence that are within N_(sep) distance from theprevious “retransmission count” channels. As illustrated, when theN_(sep) is increased, the percentage of adjacent channel interferenceincreases exponentially.

SUMMARY

In accordance with an embodiment an apparatus is disclosed. Theapparatus includes a transceiver unit, and a processing unit coupled tothe transceiver. The processor unit is configured to transmit datapackets via the transceiver unit using a frequency hopping sequence in awireless communication network, the frequency hopping sequence includesa plurality of transmission channel numbers, and adjacent transmissionchannel numbers within a predetermined number of consecutivetransmission channel numbers in the frequency hopping sequence are atleast a predetermined distance apart.

In accordance with another embodiment an apparatus is disclosed. Theapparatus includes, a transceiver; and a processing unit coupled to thetransceiver. The processing unit is configured to generate a firstfrequency hopping sequence of transmission channel numbers fortransmission in a wireless communication network, determine whether adistance between adjacent transmission channel numbers within apredetermined number of consecutive channel numbers in the firstfrequency hopping sequence of transmission channel numbers is less thana predetermined threshold distance, if the distance between adjacenttransmission channel numbers within the predetermined number ofconsecutive channel numbers in the first frequency hopping sequence isless than the predetermined threshold distance, rearrange the firstfrequency hopping sequence of transmission channel numbers to generate asecond frequency hopping sequence of transmission channel numbers, andtransmit data packets in the wireless communication system using thesecond frequency hopping sequence of transmission channel numbers.

In accordance with another embodiment a method is disclosed. The methodincludes generating by a processing unit, a first frequency hoppingsequence of transmission channel numbers for transmission in a wirelesscommunication network, determining by the processing unit whether adistance between adjacent transmission channel numbers within apredetermined number of consecutive channel numbers in the firstfrequency hopping sequence of transmission channel numbers is less thana predetermined threshold distance, if distance between adjacenttransmission channel numbers within the predetermined number ofconsecutive channel numbers in the first frequency hopping sequence oftransmission channel numbers is not equal to at least the predeterminedthreshold distance, rearranging by the processing unit the firstfrequency hopping sequence of transmission channel numbers to generate asecond frequency hopping sequence of transmission channel number, andtransmitting by the processing unit data packets in the wirelesscommunication system via a transceiver unit using the second frequencyhopping sequence of transmission channel numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a conventional implementation of LinearFeedback Shift Register scheme with inter channel interference.

FIG. 2 illustrates an exemplary system for wireless communication usingenhanced channel hopping sequence according to an embodiment.

FIG. 3 illustrates an exemplary flow diagram for generating frequencyseparated channel hopping sequence according to another embodiment.

FIG. 4A illustrates an example of distribution of channels using apseudo random sequence generated by Linear Feedback Shift Register(LFSR) method.

FIG. 4B illustrates an example of distribution of channels using apseudo random sequence generated by Linear Feedback Shift Register(LFSR) method and separated by Frequency Separated Sequence (FSS)method.

FIG. 5A illustrates an exemplary distribution plot of channels usingLFSR sequence.

FIG. 5B illustrates an exemplary distribution plot of channels usingLFSR sequence separated by FSS.

DETAILED DESCRIPTION

The following description provides many different embodiments, orexamples, for implementing different features of the subject matter.These descriptions are merely for illustrative purposes and do not limitthe scope of the invention. Specific examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting.

Referring to FIG. 2, an exemplary system 100 for wireless communicationis illustrated according to an embodiment. System 100 includes twowireless communication devices 120 and 150. Each device includes aprocessing unit (122, 152), a transceiver (124, 154), an antenna system(130, 140), and a storage unit (126, 156). Each device may further becoupled to optional external peripheral systems/components (128, 158).The system units illustrated here are for explanatory purposes only.Devices 120 and 150 can also include various other components and unitssuch as multiple processing units, display, keyboard or other userinterface mechanisms, multiple antennas, multiple storage devices, andvarious other elements needed for devices to function in a givenapplication. Further, devices 120 and 150 can be any wirelesscommunication devices such as wireless phones, computers with wirelesscommunication capability, point-of-sale units, industrial control units,smart meters, printers, or any other device, system, or the likesuitable for wireless communication application. Devices 120 and 150 cancommunicate with each other via wireless communication link usingvarious different wireless communication protocols such as Bluetooth,IEEE 802.15, WiFi, and others. In an exemplary embodiment, devices 120and 150 communicate with each other using frequency hopping or channelhopping schemes.

When device 120 communicates with the device 150, the processing unit122 can process data to be communicated to device 150. Processing unit122 can generate various data packets according to any givencommunication protocol application and then control the transceiver 124to process and transmit data packets to device 150 using antenna 130.When the transceiver 154 of device 150 receives the data packet viaantenna 140, it processes and forwards data packets to the processingunit 152 for further processing. When channel hopping scheme is used forcommunication between the device 120 and the device 150, the processingunit 122 of device 120 establishes a communication session with thedevice 150 by initiating session parameter exchange with the device 150.The session parameter exchange establishes certain understanding betweenthe two devices as to protocols and parameters that can be used for thecommunication session. The communication session can be establishedaccording to procedures defined by the communication protocol used forthe particular communication session.

According to another embodiment, when devices 120 and 150 use channelhopping scheme for communication, then the transmitting device (e.g.,device 120) generates a pseudo random sequence of transmission channelnumbers for channel hopping using known methods such as a standard hashfunction or the like. In conventional schemes, a transmitting devicetransmits parameters for generating the pseudo random sequence and othertransmission parameters to the receiving device during the sessioninitiation message exchange and then retransmits these parameters to thereceiver according to the communication protocol used for transmission.For example, for Time Slotted Channel Hopping (TSCH) scheme, parametersare repeatedly transmitted in periodic beacons. For asynchronous channelhopping, parameters are transmitted to receiver randomly in certaincontrol messages.

In conventional systems, a transmitter generates a random channelhopping sequence and then transmits parameters for generating the randomchannel hopping sequence to a receiver. The receiver uses parameters togenerate the same random channel hopping sequence as the transmitter toalign on the channel to be used for transmitting and receiving datapackets. The random channel hopping sequence may include adjacentchannel numbers that are also physically adjacent in the frequencybands. For example, the random frequency hopping sequence may includechannel numbers 2 and 3 as adjacent channel numbers in the frequencyhopping sequence; however, channel 2 and 3 may also be physicallyadjacent in the transmission frequency band. If one of the channels, saychannel 2, is noisy and a packet is transmitted in channel 2 and drops,then the transmitter will retransmit the packet in channel 3, which isnext in the sequence regardless of the channel interference experiencedby previous packet in channel 2, which may also affect transmission inchannel 3. As explained hereinabove, this can cause high error rates andperformance degradation if random channels are placed closed to eachother and retransmission occurs in a channel that is closer to a noisychannel.

According to exemplary embodiment, when device 120 establishescommunication with the device 150, the device 120 generates a pseudorandom channel hopping sequence for transmission and then createsanother frequency separated channel hopping sequence from the pseudorandom channel hopping sequence. The resulting frequency separatedchannel hopping sequence is also random; however, it is rearranged basedon certain parameters to ensure that adjacent channel numbers are atleast some distance apart so if a data packet is dropped or not receivedby the receiver due to some channel interference, then theretransmission of the packet occurs on a channel that is at least agiven distance away from the previous channel. The retransmissionchannel is then not affected by the interference of the previoustransmission channel and the throughput of the system increasessignificantly.

The distance between adjacent channels can be determined based onvarious different factors. In another embodiment, the number of times adata packet can be retransmitted according to the communication systemtransmission protocol, is used as a distance measure for a number ofconsecutive channels to be rearranged in the enhanced frequency hoppingsequence. For example, if the communication system protocol limits theretransmission of data packets to ‘N’ times, then the distance betweenchannels within ‘N’ number of consecutive channels in the enhancedfrequency hopping sequence can be adjusted to ensure they are at leastsome predetermined threshold distance apart from each other and thus arenot affected by inter-channel interference for retransmission. Avariation of parameter ‘N’ can also be used as a measure of the numberof consecutive channels to be analyzed such as N+X, N−X, N/X, or N*X,where X can be any number chosen for a particular system implementation

In other embodiment, N−1may be used as the number of consecutivechannels to be reviewed and rearranged in the random frequency hoppingsequence to ensure channel numbers within N−1 number of consecutivechannel numbers in the frequency hopping sequence are not within apredetermined distance from each other so they are not affected by theinter-channel interference. The number ‘N’ or variation thereof can beused by device 120 as a parameter or a threshold to determine whetherthe distance between adjacent channels within ‘N’ (or combinationthereof) consecutive channels in the frequency hopping sequence is suchthat they will not be affected by inter-channel interference from eachother. The distance between channels to avoid inter-channel interferencewithin a given number of consecutive channels in the enhanced frequencyhopping sequence can be predetermined based on channel conditions andsystem environment or it can be dynamically adjusted by the system basedon the history of packet loss for particular given channel or channelperformance measurements.

In exemplary implementation, if the system retransmission limit is three(3), then for a given channel number ‘Y’, if next three channels fromchannel ‘Y’ in the frequency hopping sequence are not a predeterminedthreshold distance apart from each other, then the device 120 canrearrange the frequency hopping sequence to ensure that each of thethree channels is at least predetermined distance away from the adjacentchannel. In an embodiment, the number of times a packet can beretransmitted ‘N’ can also be used as the distance between adjacentchannels in the enhanced frequency hopping sequence. In some otherembodiment, the distance between adjacent channels in the number ofselected consecutive channels can be any variation of ‘N’ thereof. Infurther embodiment, the ‘N’ can be based on the maximum expectedadjacent channel leakage, for example, in a particular system, if anoisy or leaky channel is expected to affect the next two channels, thenthe value of ‘N’ can be greater than two to ensure that two adjacentchannels in the sequence are at least two channels distance apart or thelike so the noisy channel does not affect the retransmission of packets.In general, the distance between two adjacent channels can be greaterthan the maximum expected adjacent channel leakage for the system toensure error free retransmission.

The threshold distance parameter and the number of consecutive channelsto be used for analysis can be communicated by device 120 to device 150(or visa-versa) during session initiation stage of the communication soboth transmitter and receiver devices can be synchronized for randomchannel hopping. Further, as explained above, the parameter or thresholdcan be transmitted periodically or asynchronously depending on the typeof channel hopping system protocol used for a particular givenimplementation of transmission between devices 120 and 150. The choiceof distance between adjacent channels can be based on various differentfactors such as the history of data packet transmission failure, errorrates, general physical environment of the transmission system (crowdedconcrete structures, remote areas, line of sight analysis, etc.), or thelike.

Referring to FIG. 3, an exemplary flow diagram 300 for an exemplarymethod of generating frequency separated channel hopping sequenceaccording to another embodiment is illustrated. The method can beperformed by any device such as transmitting devices 120 or 150.Initially, at 302, the device generates a pseudo random sequence (PSR)for channel hopping. At 305, an empty Frequency Separated Sequence (FSS)and Skipped Channel List (SCL) is created in the memory by the device.At 310, the device selects a channel from SCL list and determines at 315whether the selected channel is within the threshold distance from theprevious channel. If the selected channel is within the thresholddistance from the previous channel, then at 340, the device adds theselected channel to SCL. If the selected channel is not within thethreshold distance from the previous channel, then at 320, the deviceadds the channel to FSS and removes it from SCL at 325. As explainedhereinabove, the threshold distance can be selected based on systemapplication.

At 330, the device selects a channel from SCL and for each channel fromthe SCL, the device determines whether the channel is within thethreshold distance from the previous channel. If the selected channel iswithin the threshold distance from the previous channel, then at 340,the device adds the selected channel to SCL. If the selected channel isnot within the threshold distance from the previous channel, then at350, the device adds the channel to FSS and at 355 determines if all thechannels from PRS have been considered for channel separation. If allthe channels have not been considered for channel separation, then thedevice continues until all channels from the PRS have been separatedfrom adjacent channel by at least the threshold distance.

The frequency separated sequences generated by the device using thismethod are also random as they are based on an initial random sequenceand channels are uniformly distributed. The frequency separated sequencecan be generated by any element of devices 120 and 150. For example, theprocessing units 122 (or 152) can generate the random sequence andseparate all channels using the method or the sequence can be generatedby the transceiver 124 (or 154), or any other system component. While anexemplary method is illustrated in FIG. 3, one skilled in the art willappreciate that using the teachings of the disclosure, other methods canbe implemented to separate channels in a random channel hoppingsequence.

Referring to FIG. 4A, an example of distribution of 129 channels using apseudo random sequence generated by Linear Feedback Shift Register(LFSR) method is illustrated. All channels are uniformly distributed;however, because the LFSR method can generate sequence with channelscloser to each other, the inter-channel interference cannot be avoided.

Referring to FIG. 4B, an example of distribution of 129 channels using apseudo random sequence generated by Linear Feedback Shift Register(LFSR) method and separated by Frequency Separated Sequence method isillustrated. As illustrated, the uniform distribution of 129 channels isstill maintained by the FSS; however, in this case, channels are notcloser to each other and the inter channel interference improvessignificantly. Although the exact number of occurrences of some channelsmay vary, the separation of adjacent channels significantly improves theinter-channel interference between adjacent transmission channels. Inthe FSS, the minimum distance between adjacent transmission channels canbe determined by the predetermined threshold and the distance betweenadjacent transmission channels then can remain the same throughout thetransmission session thus, improving the inter-channel interference andoverall transmission system performance. Because the method forseparating adjacent transmission channels is deterministic, the methodcan be repeated for the same sequence.

Following is an example of sequence generate by an LFSR method and thenseparated by FSS method.

-   A sequence of length 512 generated using the LFSR method for 129    channels is given below:-   127 128 64 32 16 6 1 63 94 112 119 58 92 109 117 123 126 63 30 15 70    33 79 104 117 57 27 78 104 50 25 77 39 20 10 3 2 66 31 16 71 36 83    40 18 72 101 113 55 92 109 55 92 46 21 9 67 96 113 121 59 28 77 101    113 121 125 61 29 79 102 49 89 109 55 26 13 69 35 80 40 85 41 21 75    38 17 7 66 98 114 57 27 12 71 98 47 88 107 54 90 45 85 41 83 106 118    59 28 14 72 34 15 72 101 51 24 12 71 36 16 8 69 35 18 9 5 3 2 128    129 65 33 17 7 4 67 34 15 6 68 99 50 25 11 6 68 32 14 70 100 115 56    28 77 39 82 41 83 40 85 107 54 27 12 4 67 96 46 86 106 118 122 61 95    46 21 75 100 48 87 108 119 58 29 79 40 18 9 67 34 82 41 21 9 5 65 33    79 38 84 105 53 91 44 20 73 99 112 119 124 125 61 95 112 54 27 78 37    19 74 35 18 72 34 82 104 50 88 107 116 121 125 127 62 31 80 38 17 73    99 50 88 44 87 42 19 74 102 49 23 76 103 52 26 13 7 4 129 127 64 97    49 23 10 70 100 48 24 75 38 84 42 19 8 69 97 49 89 43 22 74 35 80    103 114 120 123 126 126 63 96 48 22 11 68 32 81 105 53 25 11 68 99    112 56 91 44 87 108 52 26 76 36 83 106 51 24 75 100 115 122 61 29 13    69 97 111 120 123 60 93 111 118 59 94 47 24 12 4 129 65 95 48 87 42    86 106 51 90 108 52 89 109 117 57 93 111 56 28 14 5 3 64 30 80 103    52 89 43 84 105 115 122 124 62 94 47 86 43 84 42 86 43 22 11 6 1 1    63 32 81 39 20 73 37 81 39 82 104 117 123 60 30 78 37 81 105 115 56    91 110 120 60 30 15 8 2 128 62 96 113 55 26 76 103 114 57 93 45 23    76 36 16 71 98 114 120 60 93 45 85 107 116 58 92 46 88 44 20 10 70    33 17 73 37 19 8 2 66 98 47 22 74 102 116 58 29 13 7 66 31 78 102    116 121 59 94 110 53 91 110 53 25 77 101 51 90 45 23 10 3 64 97 111    54 90 108 119 124 62 31 14 5 65 95 110 118 122 124 125-   The corresponding FSS sequence using a separation parameter of 2 is    shown below:-   127 64 32 16 6 1 128 94 63 112 119 58 92 109 117 123 126 63 30 15 70    33 79 104 117 57 27 50 78 25 104 77 39 20 10 3 66 31 16 71 36 2 83    40 18 101 72 113 55 92 109 46 21 9 55 67 92 96 113 121 59 28 77 101    113 121 125 61 29 79 102 49 89 109 55 26 13 69 35 80 40 85 21 75 38    17 41 7 66 98 114 57 27 12 71 98 47 88 107 54 90 45 85 41 83 106 118    59 28 14 72 34 101 51 24 15 12 72 71 36 16 8 69 18 5 35 3 128 9 65    33 17 7 2 4 129 67 15 34 99 50 6 25 11 68 6 68 32 14 70 100 115 56    28 77 39 82 41 85 107 54 27 83 12 40 4 67 96 46 86 106 118 122 61 95    46 21 75 100 48 87 108 119 58 29 79 40 18 9 67 34 82 41 21 9 5 65 33    79 38 84 105 53 91 44 20 73 99 112 119 124 61 95 54 112 27 78 125 37    19 74 35 72 82 104 18 50 88 34 107 116 121 125 127 62 31 80 38 17 73    99 50 88 44 42 19 74 102 87 49 23 76 52 26 103 13 7 4 129 127 64 97    49 23 10 70 100 75 48 38 24 84 42 19 8 69 97 49 89 43 22 74 35 80    103 114 120 123 126 63 96 48 22 11 26 68 32 81 105 53 25 11 68 99    112 56 91 44 87 108 52 26 76 36 83 106 51 24 75 100 115 122 61 29 13    69 97 111 120 123 60 93 118 111 47 24 12 59 4 94 129 65 95 48 87 42    106 51 90 108 86 117 57 93 52 111 89 28 109 14 5 56 3 64 30 80 103    52 89 43 84 105 115 122 124 62 94 47 86 43 84 22 11 6 86 1 42 43 63    32 81 39 20 1 73 37 104 81 82 117 39 123 60 30 78 37 81 105 115 56    91 110 120 60 30 15 8 2 128 62 96 113 55 26 76 103 57 114 93 45 23    76 36 16 71 98 114 120 60 93 45 85 107 116 58 92 46 88 44 20 10 70    33 17 73 37 19 8 2 66 98 47 22 74 102 116 58 29 13 7 66 31 78 102    116 121 59 94 110 53 91 25 77 101 110 51 53 45 90 23 10 3 64 97 111    54 90 108 119 124 62 31 14 5 65 95 110 118 122 124 127

As it can be seen from the above example that initially in the randomsequence generated using the LFSR method, channels 127 and 128 end upbeing adjacent channels in the random sequence. Similarly, channel 3 and2 are also adjacent channels among various other combinations. After theapplication of the method, the random sequence is rearranged to separateadjacent channels in the random sequence. This results in uniformchannel distribution; however, adjacent transmission channels areseparated by a distance of at least 2, avoiding inter-channelinterference.

Referring to FIG. 5A, an exemplary distribution plot of channels usingLFSR sequence is illustrated. In this example, 16 channels were used fortransmission, the number of retransmission of packets was limited to 6,and the number of channels to be separated was within a distance of 2.

Referring to FIG. 5B, an exemplary distribution plot of channels usingLFSR sequence and then separated by FSS method is illustrated. As can beseen form FIGS. 5A and 5B, the distribution of channels remains thesame; however, in the example of FIG. 5B, the inter-channel interferencewas improved by at least 80%.

The foregoing outlines features of several embodiments so that those ofordinary skill in the art may better understand various aspects of thepresent disclosure. Those of ordinary skill in the art should appreciatethat they may readily use the present disclosure as a basis fordesigning or modifying other processes and structures for carrying outthe same purposes and/or achieving the same advantages of variousembodiments introduced herein. Those of ordinary skill in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the present disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the present disclosure.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter of the appended claims is not necessarily limited tothe specific features or acts described above. Rather, the specificfeatures and acts described above are disclosed as example forms ofimplementing at least some of the claims. Various operations ofembodiments are provided herein. The order in which some or all of theoperations are described should not be construed to imply that theseoperations are necessarily order dependent. Alternative ordering will beappreciated having the benefit of this description. Further, it will beunderstood that not all operations are necessarily present in eachembodiment provided herein. Also, it will be understood that not alloperations are necessary in some embodiments.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Also,although the disclosure has been shown and described with respect to oneor more implementations, equivalent alterations and modifications willoccur to others of ordinary skill in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure comprises all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method comprising: generating, by a firstdevice, a sequence of frequencies for transmission of data between thefirst device and a second device; selecting a subset of frequencies thatare arranged consecutively in the sequence of frequencies, wherein acount of frequencies in the subset of frequencies is based on a limit ona number of retransmission attempts; determining whether each frequencyin the subset of frequencies is at least a channel threshold distanceaway from each other frequency in the subset of frequencies; and inresponse to a first frequency of the subset of frequencies being lessthan the channel threshold distance away from a second frequency of thesubset of frequencies, rearranging the sequence of frequencies such thateach frequency in the subset of frequencies is at least the channelthreshold distance away from each other frequency in the subset offrequencies.
 2. The method of claim 1 further comprising, transmitting,by the first device to the second device, the count of frequencies inthe subset and the channel threshold distance.
 3. The method of claim 2further comprising, transmitting the count of frequencies in the subsetand the channel threshold distance during a session initiation.
 4. Themethod of claim 2 further comprising, transmitting the count offrequencies in the subset and the channel threshold distance at periodicintervals.
 5. The method of claim 1 further comprising, transmitting, bythe first device to the second device, a set of data packets accordingto the sequence of frequencies.
 6. The method of claim 5, wherein thetransmitting of the set of data packets according to the sequence offrequencies uses at least one of: Bluetooth, IEEE 802.15, or Wi-Fiwireless communication protocol.
 7. The method of claim 1, wherein thesequence of frequencies is a pseudo random sequence of frequencies. 8.The method of claim 1, wherein the channel threshold distance is basedon the limit on the number of retransmission attempts.
 9. The method ofclaim 8, wherein the channel threshold distance is from a groupconsisting of: the limit on the number of retransmission attempts andthe limit on the number of retransmission attempts minus one.
 10. Themethod of claim 1, wherein the channel threshold distance is based on atleast one of: a history of packet loss, a maximum expected adjacentchannel leakage, or a physical environment of the first device.
 11. Themethod of claim 1, wherein the count of frequencies in the subset is atleast three.
 12. A device, comprising: a transceiver operable totransmit data packets; and a processing unit coupled to the transceiver,the processing unit operable to: generate a sequence of frequencies fortransmission of data by the transceiver; select a subset of frequenciesthat are arranged consecutively in the sequence of frequencies, whereina count of frequencies in the subset is based on a limit on a number ofretransmission attempts; and arrange the sequence of frequencies suchthat each frequency in the subset of frequencies is at least a channelthreshold distance away from each other frequency in the subset offrequencies.
 13. The device of claim 12, wherein the processing unit isoperable to cause the transceiver to transmit the count of frequenciesin the subset and the channel threshold distance.
 14. The device ofclaim 12, wherein the processing unit is operable to cause thetransceiver to transmit a set of data packets according to the sequenceof frequencies.
 15. The device of claim 14, wherein the processing unitis operable to cause the transceiver to transmit the set of data packetsaccording to at least one of: Bluetooth, IEEE 802.15, or Wi-Fi wirelesscommunication protocol.
 16. The device of claim 12, wherein the sequenceof frequencies is a pseudo random sequence of frequencies.
 17. Thedevice of claim 12, wherein the channel threshold distance is based onthe limit on the number of retransmission attempts.
 18. The device ofclaim 17, wherein the channel threshold distance is from a groupconsisting of: the limit on the number of retransmission attempts andthe limit on the number of retransmission attempts minus one.
 19. Thedevice of claim 12, wherein the channel threshold distance is based onat least one of: a history of packet loss, a maximum expected adjacentchannel leakage, or a physical environment of the device.
 20. The deviceof claim 12, wherein the count of frequencies in the subset is at leastthree.